llvm dev - Apr 2019 - GVN-Hoist test case not working

Hello,

I was trying a basic example on LLVM GVN Hoist and output differs from what
I expect. Am I missing something ?

*Code* :

int main()
{
int x = 7;
int a = 0;
if(a == 7){
x = 1;
a = 8 * x;
} else {
x = 1;
a = 2 * x;
}
return 0;
}

*Commands* :
clang-8 -O0 -S -emit-llvm test.c
opt-8 -gvn-hoist -S < test.ll

*Output :*

; ModuleID = '<stdin>'
source_filename = "test.c"
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"

; Function Attrs: noinline nounwind optnone uwtable
define dso_local i32 @main() #0 {
  %1 = alloca i32, align 4
  %2 = alloca i32, align 4
  %3 = alloca i32, align 4
  store i32 0, i32* %1, align 4
  store i32 7, i32* %2, align 4
  store i32 0, i32* %3, align 4
  %4 = load i32, i32* %3, align 4
  %5 = icmp eq i32 %4, 7
  br i1 %5, label %6, label %9

; <label>:6:                                      ; preds = %0
  store i32 1, i32* %2, align 4
  %7 = load i32, i32* %2, align 4
  %8 = mul nsw i32 8, %7
  store i32 %8, i32* %3, align 4
  br label %12

; <label>:9:                                      ; preds = %0
  store i32 1, i32* %2, align 4
  %10 = load i32, i32* %2, align 4
  %11 = mul nsw i32 2, %10
  store i32 %11, i32* %3, align 4
  br label %12

; <label>:12:                                     ; preds = %9, %6
  ret i32 0
}

attributes #0 = { noinline nounwind optnone uwtable
"correctly-rounded-divide-sqrt-fp-math"="false"
"disable-tail-calls"="false"
"less-precise-fpmad"="false"
"min-legal-vector-width"="0"
"no-frame-pointer-elim"="true"
"no-frame-pointer-elim-non-leaf"
"no-infs-fp-math"="false"
"no-jump-tables"="false"
"no-nans-fp-math"="false"
"no-signed-zeros-fp-math"="false"
"no-trapping-math"="false"
"stack-protector-buffer-size"="8"
"target-cpu"="x86-64"
"target-features"="+fxsr,+mmx,+sse,+sse2,+x87"
"unsafe-fp-math"="false"
"use-soft-float"="false" }

!llvm.module.flags = !{!0}
!llvm.ident = !{!1}

!0 = !{i32 1, !"wchar_size", i32 4}
!1 = !{!"clang version 8.0.0-svn356034-1~exp1~20190313093039.54
(branches/release_80)"}

Thank you,
Digvijay
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On Mon, 8 Apr 2019 at 12:22, Digvijay Gour via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> I was trying a basic example on LLVM GVN Hoist and output differs from what
I expect. Am I missing something ?
At -O0 Clang usually attaches the "optnone" attribute to functions it
generates, which disables all LLVM passes even if they get run. Try
adding "-Xclang -disable-O0-optnone" to the Clang command line.

Cheers.

Tim.

It works!
Thank You

On Mon, Apr 8, 2019 at 6:21 PM Tim Northover <t.p.northover at gmail.com>
wrote:
> On Mon, 8 Apr 2019 at 12:22, Digvijay Gour via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > I was trying a basic example on LLVM GVN Hoist and output differs from
> what I expect. Am I missing something ?
>
> At -O0 Clang usually attaches the "optnone" attribute to
functions it
> generates, which disables all LLVM passes even if they get run. Try
> adding "-Xclang -disable-O0-optnone" to the Clang command line.
>
> Cheers.
>
> Tim.
>
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